Accessing Elements I
a[index]
Element Reference - return the element at index of array a
a[n..length]
Element Reference - return subarray starting at 'n' and ending at length of array a
a.fetch(index)
Try to return element at position index of array a, but throw IndexError if index out of bounds
a.first
Return first element of array a
a.index(obj)
Find index of first obj in a where object in a == obj (option 1)
a.last
Return the last element of array a
a.sample(n)
Chose a random element or n random elements from array a
Iterating I
a.cycle(n)
Call given block for each element n times or forever if nil is given of array a
a.each
Call the given block once for each element in array a
a.each_index
Call the given block once for each element in a passing the index as param
a.map
Create a new array containing values returned by block of a (option 1)
a.reverse_each
Same as a.each, but traverses a in reverse order
Adding Items I
a << obj
Append - push obj on to the end of array a and return a
a[index] = obj
Element Assignment - set element at index to obj of array a
a1[start, length] = a2
Element Assignment - replace subarray from start to length of array a1 with a2
a1.concat(a2)
Appends the elements of a2 to a1
a.fill(obj)
Fill array a with obj
a.fill(obj, start, length)
Fill array a with obj from start to length
a.insert(index, obj)
Insert given obj before element at given index of array a
a.push(obj)
Append - push given obj on to end of array a
a.unshift(obj)
Prepend object to front of a, moving other elements upwards
Removing Items I
a.clear
Remove all elements from a
a.compact
Return a copy of a with all nil elements removed
a.compact!
Modify array a by removing nil elements from array a
a.delete(obj)
Delete all items from array a that are equal to obj
a.delete_at(index)
Delete element at index of array a, returning that element, or nil if index is out of range
a.drop(n)
Drop first n elements from array a and return the rest of the elements in an array
a.pop
Remove the last element from array a and return it, or nil if a is empty
a.pop(n)
Remove and return an array of last n elements (or less) of array a
a.shift
Remove the first element of array a and return it (shifting all other elements down by 1)
Obtaining Information I
a.any?
Return true if block returns a value other than false or nil of array a
a.count
Return the number of elements of a
a.count(obj)
Return the number of elements in a which equal obj
a.empty?
Return true if array a contains no elements
a1.eql?(a2)
Return true if a1 and a2 are the same object or both have same content
a.frozen?
Return true if array a if frozen
a.include?(obj)
Return true if given obj is present in array a
a.length
Return the number of elements in array a (may be zero)
a.size
Same as a.length
Transforming I
a.flatten
Return new array that is a one-dimensional flattening of a
a.join(separator)
Return a string of a separated by given separator (empty string by default)
a1.replace(a2)
Replace contents of a1 with a2, truncating or expanding if necessary
a.reverse
Return a new array containing a's elements in reverse order
a.rotate(count)
Return a new array by rotating a so element at count if first element in new array
a.shuffle
Return a new array with elements of a shuffled
a.sort
Return a new array created by sorting array a
a.uniq
Return a new array by removing duplicate values of array a
Selecting Items I
a.delete_if
Delete every element of array a which block evaluates to true
a.drop_while
Drop elements up to, but not including, the first element for which bock returns nil or false
a.keep_if
Delete every element of array a for which given block evaluates to false
a.reject
Return a new array containing the items in a for which the given block is not true
a.reject!
Equivalent to a.delete_if, deleting elements from a for which the block evaluates to true, but returns nil if no changes were made
a.select
Return a new array containing all elements of a for which given block returns true
a.select!
Same as a.keep_if, deleting every element of array a for which given block evaluates to false
Mathematical Operators I
a1 & a2
Set Intersection - return a new array containing elements common to arrays a1 and a2
a * int
Return a new array built by concatenating int copies of array a
a * str
Repetition - With string arg str, equivalent to a.join(str)
a1 + a2
Concatenation - return a new array by concatenating a1 and a2
a1 - a2
Difference - return a new array that is a copy of the original array a1, removing any items from array a2
a1 | a2
Set Union - return a new array by joining a1 with a2, excluding any duplicates
General I
a1 <=> a2
Comparison - return -1, 0, or +1 if a1 is less than, equal to, or greater than a2
a1 == a2
Equality - return true if a1 and a2 are the same length and each element is equal to corresponding element in the other array
a.hash
Compute a hash-code for array a
a1.initialize_copy(a2)
Replace contents of a1 with contents of a2, truncating or expanding if necessary
a.to_s
Create string representation of array a
a.to_h
Return hash of a treating array a as array of [key,value] pairs
Accessing Elements II
a[range]
Element Reference - return subarray specified by range of array a
a.first(n)
Return first n elements of array a (option 1)
a.last(n)
Return the last n elements of array a
a.rindex(obj)
Return index of last object in a == obj
a.take(n)
Return first n elements from array a (option 2)
a.take_while
Pass elements to block until block returns nil or false, then return prior elements of a
a.values_at(i1, i2, i3)
Return array containing elements of array a corresponding to given indices i1, i2, and i3
Transforming II
a.flatten!
Modify array a so that it is a one-dimensional flattening of itself
a.reverse!
Reverse array a in place
a.rotate!(count)
Rotate a in place so element at count comes first, and return a
a.shuffle!
Shuffle elements in a in place
a.sort!
Sort array a in place
a.uniq!
Remove duplicate elements from a
Iterating II
a.collect
Create a new array containing values returned by block of a (option 2)
a.collect!
Invoke given block once for each element of a, replacing the element with the value returned by the block (option 2)
a.find_index(obj)
Find index of first obj in a where object in a == obj (option 2)
a.map!
Invoke given block once for each element of a, replacing the element with the value returned by the block (option 1)
Accessing Elements III
a.assoc(obj)
Return first contained array of a whose first element is obj
a.bsearch
Find a value in array a using binary search
a.combination(n)
Return array containing all combinations of length n of a
a.permutation(n)
Yield all permutation of length n of elements of array a
a.rassoc(obj)
Return first contained array of a whose second element is obj
a.repeated_combination(n)
Yield all repeated combinations of length n of elements in array a
a.repeated_permutation(n)
Yield all repeated permutation of length n of elements in array a
Transforming III
a.pack(aTemplateString)
Pack contents of a into binary sequence according to directives in aTemplateString
a1.product(a2, a3)
Return an array of all combinations of elements from a1, a2, and a3
a.sort_by!
Sort array a in place using set of keys generated by mapping values of a through given block
a.transpose
Transpose rows and columns of array of arrays a
a.zip
Convert any arguments to arrays, then merge elements of array a with corresponding elements from each arg
